In the United States, approximately one third of adult women are trying to lose weight. Most weight losses are not sustained and in fact may be followed by gains of at least as much weight as was intentionally lost. It is unclear whether there are adverse outcomes associated with multiple intentional weight losses. The major aim of this project is to quantify the association between multiple intentional weight losses (i.e., weight fluctuations) and the development of hypertension and diabetes mellitus among 50,790 female nurses participating in the ongoing Nurses' Health Study II. In addition to assessing the consequences of weight fluctuations, their correlates and course will be identified. Among these women, 4.4% report losing 20 or more pounds three or more times or 50 or more pounds at least once. To prospectively assess the risk of developing hypertension the investigators state they will have greater than 90% power using the first 2-year follow-up cycle. Because diabetes mellitus is less common, they state that they will need three follow-up cycles to have sufficient power. A prospective study that assesses the intentionality of weight loss and does not rely on prevalent cases or long-term recall of weight, weight loss intentions, and disease diagnosis is necessary to elucidate the relation of weight fluctuations to chronic disease morbidity. No previous studies have assessed the risk of developing disease associated with multiple weight losses, independent of the effects of important confounders such as smoking, intentionality of the weight loss, physical activity, relative weight, and weight change. The investigators point out that if intentional weight loss, one time or multiple times, is associated with increased morbidity, the public health implications are enormous. Instead of counseling overweight people to lose weight, efforts would need to be placed on preventing weight gain because both excessive weight gain and weight loss would be associated with increased risk. Conversely, if only unintentional weight loss is associated with increased risk, then the current recommendations for overweight people to lose weight or at least not gain weight would be appropriate.